Contractor added 5k to final bill?

[Marty Calhoun]

I have been working with this contractor for over 5 months on our rehab.  We have spent over 100k on this rehab and made some changes through the process but we always discussed the cost of any changes.  I don't have a problem paying for work but it was my understanding that the added items were included, because anytime we asked for additional work to be done that was out of scope of the initial estimate, he always stated, he would need more money.  My final payment was to be $3500 but his bill was $8400, I would be willing to pay additionally $1640 to cover some of the work we added.  None of the items he has added were in the initial est or ever stated there would be added cost.  I want to be fair but I don't want to get screwed either.  There are still some remaining items that need to be completed.  Any advise or comments would helpful.